Vitamin C Flashcards
SVCT1
Sodium-dependent vitamin C transporter 1
Absorption of vitamin C occurs in the SI via this main transporter
Bioavailability of vitamin C
80% or greater at doses up to 100 mg/day, but less than 50% at doses up to 1250 mg/day
How does vitamin C circulate in the blood?
Freely
SVCT2
Facilitates peripheral tissue uptake of vitamin C
(T/F) Peripheral tissues can take up the oxidized form of vitamin C.
TRUE
Oxidized form = DHAA(dehydroascorbic acid)
via GLUTs 1-4 (competitive with glucose)
What is the oxidized form of vitamin C?
DHAA (Dehydroascorbic acid)
What is the reduced/active form of vitamin C?
Ascorbic acid
Thioredoxin reductase
Reduces DHAA to ascorbic acid in the peripheral tissues
Recycles vitamin C
What is essential for proper collagen formation?
Crosslinking of microfibrils
The triple helix requires what?
Hydroxylation of selected PROLINE and LYSINE residues of the chains (which requires vitamin C).
Ascorbate reduces what, which will serve as a cofactor for which two enzymes?
IRON
Lysyl hydroxylase, Prolyl hydroxylase
How is the fibril formed?
- Crosslinking of microfibrils
- Triple helix requires hydroxylation of PROLINE and LYSINE residues (requires vitamin C)
- This allows for the collagen molecule to be formed, packing the molecule will occur, creating the fibril
What happens when the fibril is not made correctly?
We do not have the hydroxylated AAs and we end up with scurvy, the CT cannot hold itself together
How does vitamin C act as an antioxidant?
Functions include:
-Regeneration of vitamin E
-Neutralizing lipid radicals
-Acting on molecular oxygen and singlet oxygen
How does vitamin C function in neurotransmitter synthesis?
Vitamin C (along with NADPH) serve as a reducing agent for dihydrobiopterin to be converted to tetrahydrobiopterin, in the reaction of TYROSINE —> L-DOPA.
It also reduces COPPER, which serves as a cofactor where DOPAMINE —> NOREPINEPHRINE via dopamine monooxygenase.
